Patterning solution deposited thin films with self-assembled monolayers

ABSTRACT

The present invention provides a method of forming a patterned thin film on a surface of a substrate having thereon a patterned underlayer of a self-assembled monolayer. The method comprises depositing a thin film material on the self-assembled monolayer to produce a patterned thin film on the surface of the substrate. The present invention further provides processes for preparing the self-assembled monolayer. The present invention still further provides solution-based deposition processes, such as spin-coating and immersion-coating, to deposit a thin film material on the self-assembled monolayer to produce a patterned thin film on the surface of the substrate.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates generally to the patterning of athin film on a surface. More particularly, the present invention relatesto a method of depositing by a solution-based technique a patterned thinfilm onto a surface that has been selectively patterned with aself-assembled molecular monolayer.

[0003] 2. Description of the Prior Art

[0004] Solution-based thin film deposition processes, such asspin-coating and immersion-coating, i.e., dip-coating, provide simple,low-cost, low-temperature routes to thin film deposition on large-areasolid substrates.

[0005] Spin-coating and dip-coating are long-tested techniques commonlyused to deposit thin films of a wide variety of materials for a broadrange of applications. These materials include, as examples, organicmaterials, such as small molecules, oligomers, polymers, andphotoresists; organic-inorganic hybrid materials; soluble inorganicmaterials, such as salts; suspensions; dispersions, such as silicaparticles or nanocrystalline materials; and metallo-organic complexes.The metallo-organic complexes may be converted to inorganic materialsupon decomposition during high temperature annealing, a process known as“metal organic deposition.”

[0006] The above thin film materials are metallic, semiconducting,insulating and superconducting. They are used in many optical,electrical, magnetic, and structural applications.

[0007] U.S. Pat. Nos. 4,916,115 and 4,952,556, both to Mantese et al.,describe patterning techniques. Thus, U.S. Pat. No. 4,916,115 describestechniques used to pattern spin-coated metallo-organic thin films bylocally pyrolyzing deposited molecules. U.S. Pat. No. 4,952,556describes techniques used to pattern spin-coated metallo-organic thinfilms by locally decomposing spin-coated metallo-organic thin films toform patterned insoluble inorganic materials upon dissolving remainingmetallo-organics in an organic solvent.

[0008] U.S. Pat. No. 5,512,131 to Kumar et al. describes a method ofpatterning a surface that employs microcontact printing, also known as“stamping,” to form patterned molecular monolayers on the surface of asubstrate.

[0009] U.S. Pat. No. 5,620,850 to Bamdad et al. describes microcontactprinting, which has been used to deposit self-assembled monolayers (SAM)that have tail groups to sense biological materials.

[0010] N. L. Abbott et al., Science, 257, 1380(1992) describes the useof self-assembled monolayers (SAM) that have tail groups to control theplacement of liquids on surfaces.

[0011] U.S. Pat. No. 6,020,047 to Everhart et al. describes the use ofself-assembled monolayers (SAM) that have tail groups as indicators ofanalytes.

[0012] U.S. Pat. No. 5,900,160 to Whitesides et al. describes the use ofpatterned monolayers as masks for etching thin films.

[0013] N. J. Jeon et al., J. Mater. Res., 10(12), 2996(1995) describesthe use of microcontact printing to prepare patterned metal-oxide thinfilms deposited from sol-gel precursors.

[0014] M. Era et al., Appl. Phys. Lett., 65, 676(1994) describesorganic-inorganic hybrid materials that form the emissive layers inlight-emitting diodes.

[0015] K. E. Paul et al., Appl. Phys. Lett., 73, 2893 (1998) describesexposure of patterned photoresist features to UV radiation.

[0016] The contents of all of the above patents and publications areincorporated herein by reference in their entirity.

[0017] For many applications, thin films must be patterned to providecontrol over the film's spatial geometry. Spin- and dip-coated thinfilms have been patterned by subtractive processes, such asphotolithography, etching, e-beam, ion-beam, or laser beam techniquesand their combinations.

[0018] Etching spin- or dip-coated thin films exposes the depositedmaterial to potentially harsh etching solutions or environments and maydegrade the desirable materials properties (e.g., electrical, optical,magnetic, or structural) of the thin film.

[0019] Etching also requires multiple processing steps making it bothmore complex and costly. For example, using photolithography to defineetch pattern requires photoresist to be applied, exposed to radiation,and developed before etching the material. In a final step, theremaining photoresist may be removed.

[0020] Interaction between the thin film material and the resist,radiation, or solvents/developer used in the lithography process mayalso degrade the deposited thin film. Accordingly, e-beam, ion-beam, orlaser beam techniques are another set of alternative routes topatterning thin films.

[0021] These focused beam techniques are serial “writing” processes thatare slow and therefore inherently more costly when large areas of thefilm must be modified. In addition, E-beam and ion-beam techniques mustbe carried out in vacuum chambers.

[0022] These techniques have been used, for example, to patternspin-coated metallo-organic thin films by locally pyrolyzing depositedmolecules, as described in the previously incorporated U.S. Pat. No.4,916,115, and by locally decomposing spin-coated metallo-organic thinfilms to form patterned insoluble inorganic materials upon dissolvingremaining metallo-organics in an organic solvent, as described in thepreviously incorporated U.S. Pat. No. 4,952,556.

[0023] These applications of focused beams to pattern thin films canlead to redeposition of undesirable materials, in the case of pyrolysis,and to possible material degradation by solvents used to remove theremaining metallo-organics, in the case of local decomposition.

[0024] In general, lithographic and focused beam techniques all requirethe use of a relatively complicated and costly apparatus to preparepatterned thin films. Resists, solvents, and developer used in theseprocesses are also consumed, thus producing undesirable waste.

[0025] Alternative routes have been explored to deposit patterned thinfilms by low cost solution processes. All of these alternativetechniques, notably ink-jet printing, screen-printing, and micromoldingdescribed herein below, have only been tested for a limited number ofmaterials systems, each giving rise to a variety of limitations.

[0026] Thus, ink-jet printing is a sequential deposition technique,making it slow and therefore, more costly. It also has limitedresolution caused by the spreading of the printed solution over thesolid substrate surface. Furthermore, it can be limited by the viscosityand flow properties of the printed solution.

[0027] In the screen-printing method, thin films are deposited byspreading a solution of material over a screen in contact with the solidsubstrate surface. As in ink-jet printing, screen-printing is typicallylimited to low resolution applications by the inability to define highresolution features in the screen mask and by restrictions on theviscosity and flow properties of the printed solution.

[0028] Micromolding in capillaries is a technique in which aninterconnected system of recessed channels, formed by placing atopographically modulated elastomeric stamp in contact with a substratesurface, is filled by capillary action on a drop of fluid containing thepre-polymer into a channel at one edge of the stamp. The pre-polymer iscured and the stamp is removed from the substrate surface, leaving aninterconnected system of microstructures.

[0029] Micromolding in capillaries is slow and can be advantageouslyused only with solvents that (1) have low viscosity and (2) do not swellthe stamp elastomer. This approach is further limited to patterningrelatively large, micron-size features over small patterned areas. Thepattern is restricted by the channel structure to extend to the edges ofthe stamp and to form interconnected and not isolated microstructures.

[0030] Microtransfer molding is a related technique in which a fluidpre-polymer is filled in indentations of a topographically modulatedelastomeric stamp, is transferred to the substrate by bringing the stampand substrate into conformal contact, and is cured to form a solid,allowing the stamp to be removed. As above, microtransfer molding islimited to large feature sizes and to materials that do not swell thestamp. An additional problem with this technique is the formation of anundesirable thin layer of material in regions where the stamp and thesubstrate surface make contact.

[0031] Thus, a need exists in the art for a simple, low-cost,low-temperature route to patterning thin films that are deposited by thewell-developed and broadly applied solution deposition techniques, suchas spin-and dip-coating, which route does not require potentiallydamaging post-deposition processing of these thin film materials.

SUMMARY OF THE INVENTION

[0032] It is an object of the present invention to provide a low-costmethod of forming a patterned thin film on a surface of a substratehaving thereon a patterned underlayer of a self-assembled monolayer.

[0033] It is another object of the present invention to providesolution-based deposition processes for depositing a thin film materialon a self-assembled monolayer to produce a patterned thin film on thesurface of the substrate.

[0034] It is a further object of the present invention to provide amethod of forming a patterned thin film on a surface of a substratewithout potentially damaging post-deposition processing.

[0035] Accordingly, the present invention provides low-cost method offorming a patterned thin film comprising: depositing a thin filmmaterial on a surface of a substrate having thereon a patternedunderlayer of a self-assembled monolayer.

[0036] The present invention further provides processes for preparingthe self-assembled monolayer as well as solution-based depositionprocesses, such as, spin-coating and immersion-coating, for depositing athin film material on a substrate having a patterned self-assembledmonolayer to produce a patterned thin film on the surface of thesubstrate.

BRIEF DESCRIPTION OF THE DRAWINGS

[0037]FIG. 1A illustrates an elastomeric stamp with indentations coatedwith a molecular species before contacting a substrate.

[0038]FIG. 1B illustrates an elastomeric stamp placed adjacent to thesubstrate such that the stamping surface contacts the substrate surface.

[0039]FIG. 1C shows the molecular species transferred to the solidsubstrate surface as a self-assembled monolayer after the elastomericstamp is removed.

[0040]FIG. 2A illustrates a dish filled with a solution of surfacederivatizing molecular species and a solid substrate immersed in thesolution.

[0041]FIG. 2B illustrates irradiation of a self-assembled molecularmonolayer using a mask.

[0042]FIG. 2C illustrates a chemically differentiated surface modifiedto a discontinuous pattern.

[0043]FIG. 3A depicts spin-coating on a substrate patterned with aself-assembled molecular monolayer to form a discontinuous thin film ina geometry defined by the inverse of the monolayer.

[0044]FIG. 3B depicts substrate having thereon a patterned thin filmafter the substrate is spun.

[0045]FIG. 3C depicts dip-coating on a substrate patterned with aself-assembled molecular monolayer to form a discontinuous thin film ina geometry defined by the inverse of the monolayer.

[0046]FIG. 3D depicts substrate having thereon a patterned thin filmafter it is withdrawn from solution.

[0047]FIG. 4 is a photograph of a patterned thin film oforganic-inorganic hybrid deposited by spin-coating on a substratepatterned with a self-assembled molecular monolayer deposited bymicrocontact printing.

DETAILED DESCRIPTION OF THE INVENTION

[0048] The present invention employs a patterned underlayer of aself-assembled molecular monolayer to selectively deposit, by solutionbased techniques, thin film materials on a solid substrate.

[0049] The self-assembled monolayer (SAM) according to the presentinvention comprises organic molecular species having functional headgroups that bind to the particular solid substrate surface and tailgroups that affect the wettability of the particular solution depositedthin films.

[0050] For example, solution deposited thin films can be obtained usingone of the solution based techniques, such as spin- orimmersion-coating, i.e., dip-coating. In the case of spin-coating, theself-assembled monolayer patterned substrate is flooded with a solutioncontaining the thin film material or its precursors and then spun toform a continuous or discontinuous thin film in a pattern defined by theself-assembled monolayer or its inverse. In the case ofimmersion-coating, the self-assembled monolayer patterned substrate isimmersed in solution containing the thin film material or its precursorsand then withdrawn from the solution to form a continuous ordiscontinuous thin film in a pattern defined by the self-assembledmonolayer or its inverse. In both of these cases, the solvent typicallyevaporates spontaneously, thereby forming the thin film. However, therate of evaporation can be accelerated by providing one or more methodsknown in the art, such as, heat, reduced pressure, ventilation, and thelike. By proper choice of concentration of material in solution, thecasting solvent, the rate of revolution for spin-coating or the rate ofsubstrate removal for dip-coating, the desired film thickness can beobtained.

[0051] The term “monolayer” has a well-defined meaning in the art, whichdefines a “monolayer” as being a single layer of atoms and/or molecules.Accordingly, the thickness of a “monolayer” cannot exceed the moleculardimensions of the constituent atoms and/or molecules.

[0052] In contrast, “thin film” according to the present invention hasplurality of layers of molecules and/or atoms, which collectively form a“thin film.”In the context of the present application the term “thinfilm” is defined as being:

[0053] (1) a thin film that is other than a monolayer, i.e., as being athin film comprising a plurality of layers of molecules and/or atoms,which collectively form a “thin film;” and

[0054] (2) a film having a thickness of from at least about 5 nm to upto about 1000 nm, preferably from at least about 10 nm to up to about300 nm, and most preferably from at least about 25 nm to up to about 100nm.

[0055] A thin film deposited by the method of the present invention isdescribed in EXAMPLE 5. This film is not a monolayer.

[0056] The thin film in the present invention can be a material, forexample, a polymer, a hybrid material, etc., which does not require achemical reaction with the substrate surface to form a thin film. Thus,there is no covalent chemical bond formed between the thin film and thesubstrate. Typically, the thin film according to the present inventionis physically adsorbed, not chemically bound, to the substrate (see, forexample, EXAMPLE 5).

[0057] In contrast, a SAM, as described in the known methods of theprior art, requires a head group that chemically binds to the substratesurface to form a monolayer, which is chemically bound to the substrateto form a monolayer that is bound to the substrate to form a singlematerial or chemical entity.

[0058] The SAM's differ from the thin films according to the presentinvention in that a SAM is a self-assembled one molecular layer. Thethin films according to the present invention have more than onemolecular layers. The thin films according to the present inventionexclude monolayers.

[0059] The thickness of the patterned thin film material can becontrolled by choosing the concentration of the thin film material orits precursors in the solution and the rate of revolution of thespinning substrate. In immersion-coating, the thickness of the patternedthin film material can be controlled by choosing the concentration ofthe thin film material or its precursors in solution and the rate ofsubstrate removal from solution.

[0060] The present invention includes a simple, low-cost,low-temperature process that allows large areas of a substrate to bepatterned in parallel without the need for post-deposition processing.Such post-deposition processing, as shown for other techniques, may havean adverse effect on the properties of the remaining thin film, therebylimiting their applications. The present invention provides a method ofdepositing patterned thin films on a variety of substrates of variousshapes, including irregularly shaped substrates.

[0061] As a substrate, any suitable material can be used. Suitablesubstrates include, for example, a metal, a metal oxide, asemiconductor, a metal alloy, a semiconductor alloy, a polymer, anorganic solid, and a combination thereof. They can be flexible orinflexible solid substrates, having a curved or planar geometry,depending on the requirements of a desired application.

[0062] The deposition, formation, and properties of self-assembledmonolayers (SAM) are active areas of scientific research. Monolayers ofmolecules are chosen with functional head groups that selectively bindto particular solid substrate surfaces and tail groups that pack andinteract with their neighbors to form relatively ordered molecularmonolayers.

[0063] Suitable molecular species that can form a self-assembledmonolayer include organic molecular species having:

[0064] (1) a head functional group capable of interaction with thesurface of the substrate forming a coated surface; and

[0065] (2) a tail group for chemical differentiation of the patternedand unpatterned regions of the coated surface.

[0066] Examples of the functional head groups that can be designed intoorganic molecules for interacting with or binding to a particularsubstrate surface with chemical specificity include one or more of thesame or different functional groups, such a phosphine, phosphonic acid,carboxylic acid, thiol, epoxide, amine, imine, hydroxamic acid,phosphine oxide, phosphite, phosphate, phosphazine, azide, hydrazine,sulfonic acid, sulfide, disulfide, aldehyde, ketone, silane, germane,arsine, nitrile, isocyanide, isocyanate, thiocyanate, isothiocyanate,amide, alcohol, selenol, nitro, boronic acid, ether, thioether,carbamate, thiocarbamate, dithiocarbamate, dithlocarboxylate, xanthate,thioxanthate, alkylthiophosphate, dialkyldithiophosphate or acombination thereof. Preferred organic compounds having head groupssuitable for use as the molecular species that can form a self-assembledmonolayer include:

[0067] (1) silanes, phosphonic acids, carboxylic acids, and hydroxamicacids, which can bind to metal oxide surfaces such as silicon dioxide,aluminum oxide, indium zinc oxide, indium tin oxide and nickel oxide;and

[0068] (2) thiols, amines and phosphines, which can bind to metalsubstrates such as gold, silver, palladium, platinum and copper and tosemiconductor surfaces such as silicon and gallium arsenide.

[0069] The tail groups can be any of the head groups, as well as ahydrocarbon, a partially halogenated hydrocarbon, a fully halogenatedhydrocarbon or a combination thereof. The hydrocarbon or the halogenatedhydrocarbon can be purely aliphatic or aromatic or can have acombination of aliphatic and aromatic groups. The halogen in thepartially or fully halogenated hydrocarbon can be one or more of thefollowing: fluorine, chlorine, bromine or iodine. Preferably, thepartially or fully halogenated hydrocarbon is a partially or fullyfluorinated hydrocarbon or a chlorofluorocarbon.

[0070] The self-assembled monolayer forms as molecules pack on andinteract with the surface of solid substrate upon contact. For example,contacting can be achieved by immersing a substrate into a solutioncontaining the desired, surface derivatizing molecular species andwithdrawing the substrate.

[0071] A monolayer can also be transferred to the surface of a substrateby dipping the substrate through a layer of molecules packed on theliquid surface of a Langmuir-Blodgett trough.

[0072] These self-assembled monolayers can be altered by exposure toradiation. For example, irradiation photochemically modifies and/orremoves molecules assembled on the substrate surface. Thus, irradiatingthe self-assembled monolayer with a patterned radiation through a mask,such as, for example, a photomask, selectively modifies exposedmolecules, producing a patterned, chemically differentiated, substratesurface. Although discussed in the context of selectively masking theoutput of the radiation source, in some embodiments a direct writingtechnique can be used to direct the radiation to desired regions to formthe patterned, chemically differentiated, substrate surface.

[0073] Alternatively, microcontact printing, also known as “stamping,”can be used to form patterned molecular monolayers on substratesurfaces. This well-developed route to form patterned surfaces isdescribed in the previously incorporated U.S. Pat. No. 5,512,131.

[0074] In one embodiment, a stamp, such as an elastomeric stamp, iscoated with an organic molecular species that interacts with or binds tothe particular solid substrate. The coated stamp is brought into contactwith and then removed from the solid substrate surface, therebytransferring a monolayer of molecules to the solid substrate surface.

[0075] Microcontact printing is a dry printing technique that typicallydoes not swell the stamp as in the case of micromolding.

[0076] Preferably, an elastomeric stamp is used to pattern planar,curved, irregularly shaped, and flexible solid substrates.

[0077] Preferably, irradiative patterning or microcontact printing isused to define patterned self-assembled monolayers prior to thin filmdeposition, for example, using a solution-based process, such as spin-or dip-coating.

[0078] The organic underlayer acts to chemically differentiate thesubstrate surface, for example providing hydrophobic versus hydrophilicregions, affecting the wettability and deposition of the solutiondeposited thin film.

[0079] In one embodiment of the present invention, a spin-coatingprocess is used. In this process, the self-assembled monolayer patternedsubstrate is flooded with a solution containing a thin film material, ora precursor of thin film material, and spun to deposit the thin filmmaterial to form a patterned thin film on the substrate.

[0080] In another embodiment of the present invention, animmersion-coating process, also known as dip-coating, is used. In thisprocess, the self-assembled monolayer patterned substrate is immersedinto a solution of the thin film material, or a precursor, withdrawingthe substrate from the solution to deposit the thin film material toform a patterned thin film on the substrate.

[0081] The tail groups in the patterned organic underlayer differentiatethe patterned and unpatterned regions of the substrate. Upon spinning orremoving the substrate from the dipping solution, a continuous ordiscontinuous thin film, patterned in the geometry of the self-assembledmonolayer or its inverse, as the case may be, depending on the chemicalnature of the self-assembled monolayer and the thin film material, isdeposited.

[0082] According to the present invention, large areas can be patternedin parallel, without the need for further post-deposition processing andthus, eliminating potentially damaging additional processing steps.

[0083] The present invention enables a wide variety of materialsincluding insulators, semiconductors, metals, and superconductors to bedeposited from solution as patterned thin films. Examples of materialsinclude organic molecules, oligomers, polymers and photoresists;organic-inorganic hybrid materials; soluble inorganic materials such assalts; dispersions such as silica particles and nanocrystallinematerials; and metallo-organic complexes that may be converted to metalsor metal oxides upon high temperature annealing.

[0084] Examples of applications of these materials include: insulatorsin electrical applications and gate insulators in transistors, forexample, prepared from organic polymers such as polyimide and polymethylmethacrylate or from metal oxides upon conversion of metallo-organics;semiconductors that form the emissive layer in light emitting diodes,the conductive channel in thin film transistors, and the photoconductivelayer in photovoltaic devices, for example, prepared from conjugatedorganic small molecules, oligomers, polymers, and organometalliccomplexes, organic-inorganic hybrid materials, and nanocrystallinematerials; metals that act as electrical wiring or contacts, forexample, made from organic conductors such as polyaniline or annealedorganometallics or metal particles yielding conductive metals ormetal-oxides; and superconductors, for example, prepared bymetallo-organic deposition from metallo-organic precursors to formYBa₂Cu₃O₇.

[0085] Optical applications include the deposition of lenses andmicrolenses, for example from polymers or silica particles; waveguidingstructures, for example from metallo-organic deposition of LiNbO₃, andphotonic band gap structures, from silica or high refractive indexparticles.

[0086] These materials have mechanical properties that make them usefulin structural applications.

[0087] Metallo-organic deposition and conversion of metal oxides can beused to form ferroelectric materials, for example, for memoryapplications; piezoelectric materials; dielectric materials, forexample, for capacitor structures; and magnetic materials, for examplefor magnetoresistive applications.

[0088] Metallo-organic deposition (MOD) is a process commonly used toprepare a wide variety of inorganic films by wet chemical techniquesusing relatively low temperatures. MOD avoids the use of vacuum or gelprocesses. Metallo-organic compounds containing the desired metallicelements are dissolved in appropriate quantities in a solvent to form asolution, which is then used to produce a thin film having apre-selected stoichiometry. The solution is applied to the substrate bya solution process, such as spin-coating or immersion-coating. The “wet”film is heated to remove solvent and decompose the metallo-organiccompound, thereby producing an inorganic film. These films can befurther annealed in appropriate environments to produce and/or controlspecific properties, such as, for example, oxygen stoichiometry, grainsize, and grain orientation.

[0089] The present invention can also be used in a hybrid lithographictechnique to reduce processing time and cost by using the method of thepresent invention to define larger scale features in photoresists incombination with more expensive, for example, e-beam lithography, usedto pattern small-scale features.

[0090] The method according to the present invention includes the stepof depositing a thin film material on the self-assembled monolayer toproduce a patterned thin film on the surface of the substrate.

[0091] Referring to FIG. 1A, elastomeric stamp 20 is prepared, forexample from polydimethylsiloxane, with at least one indentation. Thetopographically modulated surface of the elastomeric stamp 20 is coatedover the entire surface of the stamp 22 with organic molecular species24.

[0092] Molecules 24 are chosen with functional head groups that bind tothe particular solid substrate surface 26. Such molecules includecompounds, such as, silanes, phosphonic acids, carboxylic acids, andhydroxamic acids, which can bind to a metal oxide surface, and thiols,amines, and phosphines, which can bind to metal and semiconductorsurfaces.

[0093] Referring to FIG. 1B, the elastomeric stamp 20 is placed in apredetermined orientation, adjacent to the substrate 26 such that onlythe stamping surface 28 contacts the substrate surface 26. Theelastomeric stamp 20 is held in contact with the substrate surface 26allowing the organic molecular species to transfer to the substratesurface 26.

[0094]FIG. 1C shows monolayer 24 transferred to the solid substratesurface 26 after the elastomeric stamp 20 is removed.

[0095] A self-assembled molecular monolayer 24 is transferred to thesolid substrate surface 26 only in the regions 28 where the elastomericstamp 20 is brought into contact with the solid substrate surface 26.Regions of the substrate surface 26 not contacted by the elastomericstamp 20 remain free of molecular species 24. Thus, the topography ofthe elastomeric stamp 20 defines the pattern of the self-assembledmolecular monolayer 24 on the solid substrate surface 26.

[0096] Choice of the tail group of the stamped molecular species 24modifies the chemical nature of the substrate surface 26. Thus,subsequent solution deposition of the thin film will be determined bythe chemical nature of the tail group and surface characteristics of thesubstrate.

[0097] Referring to FIG. 2A, dish 30 filled with a solution of thedesired surface derivatizing molecular species 32 can be seen. The solidsubstrate 34 is immersed in the solution of molecules 32 for a timeperiod long enough to allow the organic molecular species of themolecules in solution 32 to come into contact with, bind to and pack onthe substrate surface 34, forming a self-assembled molecular monolayer40.

[0098] Referring to FIG. 2B, radiation 36 is spatially modulated inintensity using a mask 38. The self-assembled molecular monolayer 40 isexposed to the radiation 36 only in regions 42 defined by thetransparent regions in the mask 38. The self-assembled molecularmonolayer 40 absorbs the incident radiation 36, such as light.Irradiation with light photochemically modifies and/or removes theexposed self-assembled molecular layer 40 in regions 42.

[0099] Referring to FIG. 2C, it is seen that local photochemistry,defined by the pattern of the mask 38, has modified the self-assembledmolecular monolayer in regions 42 shown in FIG. 2B to produce thechemically distinct surface 44. The chemically differentiated surface 44is in contrast to the chemical nature of the original molecularmonolayer 40, which now has a discontinuous pattern.

[0100] The self-assembled molecular monolayers, deposited and defined bythe examples of microcontact printing and self-assembly/irradiativepatterning, provide chemical differentiation between patterned andunpatterned regions of the substrate surface that affect the wettabilityand therefore the subsequent deposition thereon, by solution basedtechniques, of patterned thin film materials.

[0101]FIG. 3A illustrates the solution deposition technique known asspin-coating. FIG. 3B depicts substrate having thereon a patterned thinfilm after the substrate is spun.

[0102] Following the deposition and patterning of the self-assembledmolecular monolayer, a solution containing the desired thin filmmaterial 60, or a precursor, is flooded across the entire substratesurface 64, pre-patterned with a self-assembled molecular monolayer 62.The tail group of the self-assembled molecular monolayer 62 is chosen toprovide chemical differentiation, for example hydrophobicity versushydrophilicity, between patterned 62 and unpatterned 66 regions of thesolid substrate surface 64. The chemical differentiation across thesubstrate surface, between 62 and 66, affects the wettability of thesolution deposited thin film so that upon spinning, the materialdeposits only in unpatterned regions 66, forming a patterned thin film68 on the substrate surface 64. The thickness of the patterned thin filmmaterial 68 is controlled by choosing the concentration of the thin filmmaterial or its precursors in the solution 60 and the rate of revolutionof the spinning substrate 64.

[0103] The process shown in FIG. 3A can be operated in an inverse modeto control the deposition of the thin film. For example, theself-assembled molecular monolayer may be chosen to increase thewettability of the solution deposited thin film in contrast to thechemical nature of the native substrate surface or a substrate surfacepatterned with a second, spatially offset, molecular layer thatdecreases the wettability of the solution deposited thin film. In thiscase, the spin-coated thin film deposits on top of the self-assembledmolecular layer and not on unpatterned regions of the substrate surfaceor the regions patterned with the second self-assembled molecular layer.

[0104]FIG. 3C illustrates the solution deposition technique known asimmersion coating, or dip-coating. Following the deposition andpatterning of the self-assembled molecular monolayer, dish 70 is filledwith a solution containing the desired thin film material or itsprecursors 72 and the substrate 74 is immersed in solution 72.

[0105] The tail group of the self assembled molecular layer 76 is chosento provide chemical differentiation between patterned 76 and unpatterned78 regions of the solid substrate surface 74. As in spin-coating case,the tail group of the self assembled molecular layer 76 affects thewettability of the dip-coated thin film. The substrate 74 is withdrawnfrom solution 72 leaving behind material only in unpatterned regions 78,forming a patterned thin film 80 on the substrate surface 74, as can beseen in FIG. 3D.

[0106] In immersion-coating, the thickness of the patterned thin filmmaterial 80 is controlled by choosing the concentration of the thin filmmaterial or its precursors in solution 72 and the rate of substrate 74removal from solution 72. In this case, the patterned thin film isdeposited in regions free from the self-assembled molecular layer 78. Asin the case of spin-coating described above, a self-assembled molecularlayer can be chosen to have a tail group that increases the wettabilityof the dip-coated thin film in contrast to the native substrate surfaceor a second, spatially offset, molecular monolayer.

[0107]FIG. 4 shows a photograph of a patterned thin film oforganic-inorganic hybrid material represented by the formula(C₆H₅C₂H₄NH₃)₂SnI₄ deposited by spin-coating on a patternedself-assembled molecular monolayer. The organic molecular species isdeposited by microcontact printing to form a self-assembled molecularmonolayer on the surface of a solid substrate. Spin-coating on thesubstrate patterned with a self-assembled molecular monolayer forms adiscontinuous thin film of the organic-inorganic hybrid in a geometrydefined by the inverse of the monolayer.

EXAMPLE 1

[0108] A template having an exposed and developed photoresist patternwas fabricated by photolithography. A 10:1 (w:w or v:v) mixture ofPDMS-Sylgard Silicone Elastomer 184 and Sylgard Curing Agent 184 (DowCorning Corp., Midland, Mich) was degassed under vacuum for about 10minutes, then the mixture was poured over the template. The PDMS curedat 65° C. within 60 minutes to produce an elastomeric stamp. Aftercooling to room temperature, the PDMS stamp was carefully peeled fromthe template. A thermally grown silicon dioxide surface on an n-typesilicon wafer was patterned with a self-assembled molecular monolayer ofoctadecyl phosphonic acid by the elastomeric stamp using microcontactprinting, as illustrated in FIGS. 1A-C.

[0109] The phosphonic acid terminal head group acts to bind to thehydrophillic silicon dioxide surface and the long octadecyl chainimparts a contrasting hydrophobic surface. Patterning the silicondioxide surface with octadecylphosphonic acid provides a substratesurface with contrasting hydrophilic and hydrophobic regions.

[0110] A solution of the organic-inorganic hybrid material,phenethylammonium tin iodide having the formula (C₆H₅C₂H₄NH₃)₂SnI₄ inmethanol was flooded across the pre-patterned substrate surface. Thesubstrate covered in a pool of solution was spun forming adiscontinuous, polycrystalline thin film of the organic-inorganic hybridmaterial.

[0111] As shown in the photograph (FIG. 4), the depositedorganic-inorganic hybrid material appears, in reflection, green on thesubstrate surface. The hybrid deposits on the hydrophilic, uncoatedregions of the silicon dioxide surface and not on the hydrophobicregions where the self-assembled molecular monolayer,octadecylphosphonic acid, was stamped. The pattern of the deposited thinfilm was defined by the topography of the elastomeric stamp used todeposit the patterned self-assembled molecular monolayer.

EXAMPLE 2

[0112] A silicon dioxide surface on an n-type silicon wafer waspatterned by microcontact printing with a self-assembled monolayer ofthe fluorinated silane having the formula (tridecafluoro1,1,2,2-tetrahydrooctyl)trichlorosilane. The trichlorosilane head groupacts to bind to the hydrophilic silicon dioxide surface and thefluorinated hydrocarbon tail group imparts a contrasting hydrophobicsurface, akin to Teflon. The chemical differentiation across thesubstrate surface was similarly used to define the pattern of depositedthin films of various organic-inorganic hybrid materials.

[0113] Each of the following organic-inorganic hybrid materials wereused:

[0114] (1) phenethylammonium tin iodide having the formula(C₆H₅C₂H₄NH₃)₂SnI₄ from a solution in methanol;

[0115] (2) butylammonium methylammonium tin iodide having the formula(C₄H₉NH₃)₂CH₃NH₃Sn₂I₇ from a solution in N,N-dimethylformamide;

[0116] (3) phenethylammonium methylammonium tin iodide having theformula (C₆H₅C₂H₄NH₃)₂CH₃NH₃Sn₂I₇ from a solution inN,N-dimethylformamide; and

[0117] (4) butanediammonium tin iodide having the formula(H₃NC₄H₈NH₃)₂SnI₄ from a solution in methanol.

[0118] These examples of organic-inorganic hybrid materials aremolecular-scale composites of organic and inorganic layers. Theflexibility in the chemistry of the hybrid materials allows thecomposition of the organic and inorganic layers and the dimensionality,i.e., number of inorganic layers per organic layer, to be tailored.

[0119] Organic-inorganic hybrid materials, as above, form the activesemiconducting channel in thin film transistors, as described in thecopending U.S. Pat. application, Ser. No. 09/261,515, filed on Mar. 3,1999, the contents of which are incorporated herein by reference in itsentirety.

[0120] The organic-inorganic hybrid materials also form the activesemiconducting channel in the emissive layers in light-emitting diodes,as described in the previously incorporated M. Era et al., Appl. Phys.Lett., 65, 676(1994).

EXAMPLE 3

[0121] As silicon dioxide surface on an n-type silicon wafer ispatterned by microcontact printing with a self-assembled monolayer of(tridecafluoro 1,1,2,2-tetrahydrooctyl)trichlorosilane (a fluorinatedsilane).

[0122] The chemical differentiation on the substrate surface is used todefine the pattern of deposited thin film of the copolymer polymethylmethacrylate/methyl methacrylate (PMMA/MMA) from a solution in ethyllactate. PMMA/MMA is used as an insulator in electrical applications andas a material to prepare microlenses for optical applications. It isalso a resist for e-beam lithography.

[0123] The method of the present invention can be used to define largefeatures in resist and e-beam lithography can be used to pattern smallfeatures. The hybrid technique resulting from the combination of thesemethods allows patterning of both large and small features on thesubstrate thereby reducing the time and the overall cost of patterningrelative to using e-beam lithography alone.

EXAMPLE 4

[0124] As silicon dioxide surface on an n-type silicon wafer waspatterned by microcontact printing with a self-assembled monolayer of(tridecafluoro-1,1,2,2-tetrahydrooctyl)trichlorosilane. Chemicallydifferentiated substrate surface was used to define the pattern ofdeposited thin film of positive, deep UV photoresist UV82, produced bythe Shipley Co., which employs ethyl lactate as the casting solvent.

EXAMPLE 5

[0125] As silicon dioxide surface on an n-type silicon wafer waspatterned by microcontact printing with a self-assembled monolayer of(tridecafluoro 1,1,2,2-tetrahydrooctyl)trichlorosilane. The chemicallydifferentiated substrate surface was used to define the pattern of athin film of 50 nm silica particles deposited from a colloidalsuspension (Highlink OG 113-53), produced by Clariant Corp, whichincorporates isopropanol and hexamethylene diacrylate as spin-castingsolvents.

[0126] Silica particles and other high index particles can be used asphotonic band gap materials to control the propagation and diffractionof light, and as lenses. Similarly, thin films of smallernanocrystalline materials, which may be for example semiconducting,metallic, superconducting, ferroelectric, and magnetic, can bepatterned.

[0127] These materials can be patterned for applications such aslight-emitting diodes, thin film transistors, photovoltaic devices,ferroelectric memory applications and storage devices.

EXAMPLE 6

[0128] A silicon dioxide surface on an n-type silicon wafer is patternedby microcontact printing with a self-assembled monolayer of(tridecafluoro 1,1,2,2-tetrahydrooctyl)trichlorosilane. The chemicallydifferentiated substrate surface is used to define the pattern of adeposited thin film of the metallo-organic complex, tin 2-ethylhexanoatefrom a toluene solution. Tin 2-ethyl hexanoate is one example of ametallo-organic complex and is commonly used as a precursor formetallo-organic deposition of the transparent semiconductor SnO₂. Themetallo-organic thin film is annealed at elevated temperatures, removingthe organic component and forming a crystallized metal-oxide thin film.Other metallo-organic complexes and their combinations may be similarlydeposited and annealed to prepare metal and metal oxide thin filmsdepending on the atmosphere during annealing. These materials are forexample metallic, dielectric, ferroelectric, piezoelectric, andsuperconducting and are used in applications such as metal wires orcontacts, layers in capacitors, waveguiding structures, components inmemory cells, and components in superconducting devices.

[0129] The present invention has been described with particularreference to the preferred embodiments. It should be understood that theforegoing descriptions and examples are only illustrative of theinvention. Various alternatives and modifications thereof can be devisedby those skilled in the art without departing from the spirit and scopeof the present invention. Accordingly, the present invention is intendedto embrace all such alternatives, modifications, and variations thatfall within the scope of the appended claims.

What is claimed is:
 1. A method of forming a patterned thin film,wherein said thin film is not a monolayer, said process comprising thestep of: depositing a thin film material on a surface of a substratehaving thereon a patterned underlayer of a self-assembled monolayer. 2.The method of claim 1, wherein said substrate is selected from the groupconsisting of: a metal, a metal oxide, a semiconductor, a metal alloy, asemiconductor alloy, a polymer, an organic solid, and a combinationthereof.
 3. The method of claim 2, wherein said substrate is anirregularly shaped substrate.
 4. The method of claim 2, wherein saidsubstrate is a solid substrate having a flexible, curved or planargeometry.
 5. The method of claim 1, wherein said self-assembledmonolayer has patterned and unpatterned regions and is prepared by aprocess comprising the steps of: providing a stamp having a surface;coating said surface of said stamp with an organic molecular species toproduce a coated surface, said organic molecular species having a headfunctional group capable of interacting with said surface of saidsubstrate, and a tail group for chemical differentiation of saidpatterned and unpatterned regions of said coated surface; placing saidcoated surface in contact with said substrate for a length of timesufficient to transfer said self-assembled monolayer of said organicmolecular species from said stamp to said substrate; and removing saidstamp.
 6. The method of claim 5, wherein said stamp is an elastomericstamp.
 7. The method of claim 5, wherein said stamp has at least oneindented and at least one non-indented surface.
 8. The method of claim7, wherein said transfer is in a pattern defined by the topography ofsaid stamp.
 9. The method of claim 5, wherein said organic molecularspecies has a functional head group selected from the group consistingof: a phosphine, phosphonic acid, carboxylic acid, thiol, epoxide,amine, imine, hydroxamic acid, phosphine oxide, phosphite, phosphate,phosphazine, azide, hydrazine, sulfonic acid, sulfide, disulfide,aldehyde, ketone, silane, germane, arsine, nitrile, isocyanide,isocyanate, thiocyanate, isothiocyanate, amide, alcohol (hydroxyl),selenol (selenide), nitro, boronic acid, ether, thioether, carbamate,thiocarbamate, dithiocarbamate, dithlocarboxylate, xanthate,thioxanthate, alkylthiophosphate, dialkyldithiophosphate, and acombination thereof.
 10. The method of claim 5, wherein said organicmolecular species has a functional tail group selected from the groupconsisting of: a hydrocarbon, partially halogenated hydrocarbon, fullyhalogenated hydrocarbon, phosphine, phosphonic acid, carboxylic acid,thiol, epoxide, amine, imine, hydroxamic acid, phosphine oxide,phosphite, phosphate, phosphazine, azide, hydrazine, sulfonic acid,sulfide, disulfide, aldehyde, ketone, silane, germane, arsine, nitrile,isocyanide, isocyanate, thiocyanate, isothiocyanate, amide, alcohol(hydroxyl), selenol (selenide), nitro, boronic acid, ether, thioether,carbamate, thiocarbamate, dithiocarbamate, dithlocarboxylate, xanthate,thioxanthate, alkylthiophosphate, dialkyldithiophosphate, and acombination thereof.
 11. The method of claim 5, wherein said organicmolecular species comprises one or more compounds selected from thegroup consisting of: a silane, a phosphonic acid, a carboxylic acid, ahydroxamic acid, a thiol, an amine, a phosphine, a hydrocarbon,partially halogenated hydrocarbon and a fully halogenated hydrocarbon.12. The method of claim 5, wherein said organic molecular speciescomprises (tridecafluoro-1,1,2,2-tetrahydrooctyl)trichlorosilane. 13.The method of claim 5, wherein said organic molecular species comprisesoctadecylphosphonic acid.
 14. The method of claim 1, wherein saidself-assembled monolayer has patterned and unpatterned regions and isprepared by a process comprising the steps of: contacting said substrateand a solution comprising an organic molecular species having a headfunctional group capable of interacting with said surface of saidsubstrate, and a tail group for chemical differentiation, saidcontacting being at a temperature and for a length of time sufficient tobind said functional head groups to said surface of said substrate; andexposing said self-assembled molecular monolayer to radiation modulatedspatially in intensity with a mask having one or more regionstransparent to radiation to chemically modify said self-assembledmolecular monolayer in a chemically distinct pattern defined by saidtransparent regions of said mask.
 15. The method of claim 14, whereinsaid radiation is light.
 16. The method of claim 14, wherein said maskis a photomask.
 17. The method of claim 14, wherein said contacting iscarried out by immersing said substrate in said solution comprising saidorganic molecular species.
 18. The method of claim 14, wherein saidorganic molecular species has a functional head group selected from thegroup consisting of: a phosphine, phosphonic acid, carboxylic acid,thiol, epoxide, amine, imine, hydroxamic acid, phosphine oxide,phosphite, phosphate, phosphazine, azide, hydrazine, sulfonic acid,sulfide, disulfide, aldehyde, ketone, silane, germane, arsine, nitrile,isocyanide, isocyanate, thiocyanate, isothiocyanate, amide, alcohol(hydroxyl), selenol (selenide), nitro, boronic acid, ether, thioether,carbamate, thiocarbamate, dithiocarbamate, dithlocarboxylate, xanthate,thioxanthate, alkylthiophosphate, dialkyldithiophosphate, and acombination thereof.
 19. The method of claim 14, wherein said organicmolecular species has a functional tail group selected from the groupconsisting of: a hydrocarbon, partially halogenated hydrocarbon, fullyhalogenated hydrocarbon, phosphine, phosphonic acid, carboxylic acid,thiol, epoxide, amine, imine, hydroxamic acid, phosphine oxide,phosphite, phosphate, phosphazine, azide, hydrazine, sulfonic acid,sulfide, disulfide, aldehyde, ketone, silane, germane, arsine, nitrile,isocyanide, isocyanate, thiocyanate, isothiocyanate, amide, alcohol(hydroxyl), selenol (selenide), nitro, boronic acid, ether, thioether,carbamate, thiocarbamate, dithiocarbamate, dithlocarboxylate, xanthate,thioxanthate, alkylthiophosphate, dialkyldithiophosphate, and acombination thereof.
 20. The method of claim 14, wherein saidself-assembled molecular monolayer comprises(tridecafluoro-1,1,2,2-tetrahydrooctyl)trichlorosilane.
 21. The methodof claim 14, wherein said self-assembled molecular monolayer comprisesoctadecylphosphonic acid.
 22. The method of claim 1, wherein said thinfilm is deposited by a solution-based deposition process.
 23. The methodof claim 22, wherein said thin film material is selected from the groupconsisting of: an organic molecule, a short-chain organic oligomer, along-chain organic polymer, a photoresist, an organic-inorganic hybridmaterial, a metallo-organic complex, a nanoparticle of metal, ananoparticle of metal oxide, a nanoparticle of semiconductor, a silicaparticle, an inorganic salt, and a mixture thereof.
 24. The method ofclaim 23, wherein said organic-inorganic hybrid material is selectedfrom the group consisting of: (C₆H₅C₂H₄NH₃)₂SnI₄, (C₄H₉NH₃)₂CH₃NH₃Sn₂I₇,(C₆H₅C₂H₄NH₃)₂CH₃NH₃Sn₂I₇, (H₃NC₄H₈NH₃)₂SnI₄ and a mixture thereof. 25.The method of claim 23, wherein said photoresist is a positive working,deep UV photoresist.
 26. The method of claim 23, wherein said long-chainorganic polymer is polymethyl methacrylate/methyl methacrylatecopolymer.
 27. The method of claim 23, wherein said metallo-organiccomplex is tin 2-ethylhexanoate.
 28. The method of claim 22, whereinsaid solution-based deposition process is a spin-coating processcomprising the steps of: flooding said substrate having thereon saidpatterned self-assembled molecular monolayer with a solution comprisinga thin film material or a precursor thereof; and spinning to depositsaid thin film material thereby forming a patterned thin film on saidsubstrate.
 29. The method of claim 22, wherein said solution-baseddeposition process is an immersion-coating process comprising the stepsof: immersing said substrate having thereon said patternedself-assembled molecular monolayer into a solution comprising said thinfilm material, or a precursor thereof; and withdrawing said substratefrom said solution, thereby forming a patterned thin film on saidsubstrate.